Document Detail

Angiotensin-converting enzyme of the human small intestine. Subunit and quaternary structure, biosynthesis and membrane association.
MedLine Citation:
PMID:  1326943     Owner:  NLM     Status:  MEDLINE    
Angiotensin-converting enzyme (ACE) was isolated from detergent-derived extracts of human intestinal brush-border membranes (BBMs) by immunoprecipitation using a monoclonal antibody. Analysis of the immunoprecipitates by SDS/PAGE revealed a polypeptide of apparent M(r) 184,000 under reducing and non-reducing conditions, indicating that ACE does not contain intermolecular disulphide bridges. The quaternary structure of ACE was examined using cross-linking experiments with dithiobis[succinimidylpropionate] (DSP) and density gradient centrifugation on sucrose gradients. Both approaches demonstrated that ACE is assembled in the membrane as a monomer. By contrast, the control glycoprotein aminopeptidase N (ApN) exists as a dimer. Biosynthetic labelling experiments in intestinal tissue explants demonstrated that the 184,000-M(r) protein is generated from a single-polypeptide, mannose-rich precursor of ACE (M(r) 175,000) by modification of the carbohydrate side-chains in the Golgi apparatus. The mode of association of the mature form of the enzyme with BBMs was investigated by hydrophobic labelling of right-side-out brush-border vesicles with the photoactivatable carbene-generating reagent 125I-labelled 3-(trifluoromethyl)-3-(m[formylamino]phenyl)diazirine (125I-labelled TID), followed by treatment with trypsin at dilutions that do not cause substantial degradation of ACE. These studies demonstrated that ACE is associated with the membrane via a hydrophobic segment. Furthermore, treatment of 35S-labelled inside-out membrane vesicles with trypsin revealed that ACE possesses a cytoplasmic tail, and therefore has a transmembraneous orientation.
H Y Naim
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  The Biochemical journal     Volume:  286 ( Pt 2)     ISSN:  0264-6021     ISO Abbreviation:  Biochem. J.     Publication Date:  1992 Sep 
Date Detail:
Created Date:  1992-10-19     Completed Date:  1992-10-19     Revised Date:  2013-06-12    
Medline Journal Info:
Nlm Unique ID:  2984726R     Medline TA:  Biochem J     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  451-7     Citation Subset:  IM    
Institute of Microbiology, Heinrich-Heine University of Düsseldorf, Germany.
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MeSH Terms
Cell Membrane / enzymology
Cross-Linking Reagents
Electrophoresis, Polyacrylamide Gel
Intestine, Small / enzymology*
Macromolecular Substances
Microvilli / enzymology
Organ Culture Techniques
Peptidyl-Dipeptidase A / chemistry,  metabolism*,  secretion
Precipitin Tests
Protein Conformation
Succinimides / chemistry
Reg. No./Substance:
0/Cross-Linking Reagents; 0/Macromolecular Substances; 0/Succinimides; 57757-57-0/dithiobis(succinimidylpropionate); EC A

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